(a) Technical Field of the Invention
The present application generally pertains to a method and device used to mitigate against soft tissue injury during joint replacement surgery. More specifically, the present application relates to a method and device for moderating injury and tissue damage that occurs when extracting a reaming tool during joint replacement surgery.
It is fundamental that, when tissue damage is minimized during the surgery process, the patient's ability to quickly regain normal levels of physical function and avoid post-operation pain and protracted rehabilitation is enhanced.
Surgically-implanted prosthetic joints are commonly used to replace an arthritic and diseased or damaged joint within the human body. For ball and socket joints, such as hip or shoulder joints, the desired result is to have an artificial ball arising from one bone, set against or secured to and articulating within an implanted artificial socket in a manner that approximates a healthy natural joint. The features and function of artificial ball and socket joints are known to those of ordinary skill in the art, and thus need not be described in detail herein.
The surgical process for implanting artificial hip joints includes the use of a tool commonly known as an acetabular grater. The acetabulum is the person's natural hip socket. The acetabular grater is used for reaming the inner surface of this acetabular socket to create a surface within the socket that is suitable for accommodating the installation of a generally concave, artificial acetabular cup and liner. A typical acetabular grater is comprised of a modular metal shell component, having a convex, substantially hemispherical geometrical configuration. A shell component, which is the acetabular grater, typically is mounted to a long metal shaft commonly known as a reamer handle, which connects along the central part of the cavity located on the backside of acetabular grater. The reamer handle forms an axis of rotation for the acetabular grater. A source of rotary power in the form of a surgical drill is connected to the reamer handle and turns the rotating portion of the reamer handle along with the acetabular grater, thus allowing the surgeon to transmit torque to achieve the cutting and grating of bone and cartilage within the joint socket.
Cutting is achieved via a plurality of sharp, raised edges located along the convex surface of the acetabular grater. Cut fragments of bone and cartilage enter, and are collected in, the body of the acetabular grater through an opening located along each of the plurality of sharp raised edges. Each shell component grater has a designated diameter. Based upon the size of the patient's natural joint socket, reaming begins with the use of an acetabular grater that is smaller than the natural joint socket, and then progresses incrementally in size until all the joint cartilage or other soft tissue or bony debris is removed, and the acetabulum is reamed to the desired size and condition. As each shell of the grater fills with bone and cartilage fragments during the reaming process, they are extracted from the joint, then the grater is changed to a larger size, and reaming resumes. The features and functions of an acetabular reaming system and all its components are known to those of ordinary skill in the art, and thus need not be described in further detail herein.
There is limited space to accommodate and accept the insertion of an acetabular grater into the surgical incision site opening during the reaming process due to soft tissues, contractures, and bone overlying and or enveloping the acetabulum. This is especially the case during total hip replacement surgeries and particularly those that are performed through an anterior surgical approach, which is typically a smaller more state of the art minimally invasive incision and technique. This makes advancing the acetabular grater into the acetabulum somewhat challenging at times. Even more challenging is extraction of this acetabular grater following its use. It is during each of these commonly difficult extractions that the backside of the prior art acetabular grater system, due to its flat shape and steep edged corners, lodges or snags and hangs up on the enveloping soft tissues and bone. This causes a significant increase in force, manipulation, and time that is needed to extract the grater, thus simultaneously causing significantly more soft tissue and vascular damage. Specifically, this relative difficulty of extraction starts a negative domino effect by increasing the time for completion of surgery, thereby increasing the time the patient is under anesthesia, which then increases unnecessary risks to the patient including but not limited to increasing the risk for unintended soft tissue and vascular damage. This also increases the physical force needed to extract the acetabular grater which then causes further damages to tissues. By default this difficult extraction then fatigues and frustrates the surgeon, and causes other related problems, not to mention that this also is increasing the financial cost to the patient and the facility all the while.
(b) Description of the Relevant Art
A considerable number of patents relate generally only to surgical acetabular reamers. Many of these inventions address the access to the acetabulum, the precision of the reaming, the removal of bone, and the connection apparatus of the reamer device. Some of these inventions attempt to decrease soft tissue damage.
In U.S. Pat. No. 8,784,422 B2, by Lechot, Desarzens, and White discloses an acetabular reamer tool for cutting a hemispherical cavity in bone. Due to the modified shape of the cutting surfaces, this device sets forth to allow for cutting of the bone more precisely. They further state that it allows the tool to be more linearly advanced without having to “rock” the tool by changing the orientation of the cutting approach in order to achieve the full cut. This is all accomplished while simultaneously employing the linear cut to be guided by accurate visual confirmation by the user.
In U.S. Pat. No. 8,235,996 B2, by Parker also discloses an acetabular reamer tool for cutting a hemispherical cavity in bone. This patent sets forth a modified shape of the reamer (grater) shell that allows it to be more low profile and only partially hemispherical. In essence, instead of the traditional prior art reamers that are fully hemispherical on their leading end that is introduced into the acetabulum (but still flat on their backside), this device is more ovular. It still follows a circumferential rotation cutting a perfectly hemispherical cavity in the bone as its prior art counterparts (because of its two remaining hemispherical ends), but its sides have been taken away and replaced by a planar or concave shape making it more ovular in overall shape. This lower profile design purports to decrease soft tissue damage upon inserting the reaming tool into the surgical site, and during reaming, and upon extraction, but due to its ovular shape it does “wobble” a little upon its axis during rotation.
U.S. Pat. No. 7,621,915 B2, by Frederick, Miller, and Walter is very similar to the Parker invention in many respects. Although they too attempt to set forth a low profile acetabular reamer that is primarily ovular in shape having the sides removed and replaced with a planar surface, it differs in its positioning of the teeth or cutting edges. Even further, in one embodiment it has a traditionally hemispherical reamer with respect to its leading edge during insertion (like the traditional prior arts), but it has removed the teeth or cutting edges completely on opposing sides so that the opposing sides of the hemisphere are smooth. The backside of the reamer shells (that connects to the reamer handle) of all the embodiments of this invention including that of the aforementioned Parker's, remain flat shaped.
U.S. Pat. No. 7,559,928 B2, by Johnson, Engh, and Travanty is an apparatus and method directed to accomplish accurate bone preparation through a limited surgical exposure for hip replacement surgeries. This is not simply a reamer but is rather a collective system comprised of multiple parts including its own reamer handle to accomplish the desired goal. Its primary delineating feature that contrasts the other prior art is that it positions the reamer shell sideways on its reamer handle. Instead of a reamer shell that is connected in a linear configuration with the reamer handle with direct axial rotation parallel to and in line with the linear reamer handle (as a traditional drill and drill bit), it positions the reamer shell and its axis of rotation perpendicular to the side of the linear shaft of the reamer handle. In doing this the reamer shell is introduced into the surgical site with its side being the leading edge. This essentially works, at least during introduction and extraction of the reamer, as do the low profile reamers of the two previously mentioned patents by introducing and extracting a tool with less surface area by the leading edge.
U.S. Pat. No. 7,220,264 B1, by Hershberger sets forth a reamer for reaming of an acetabulum during a minimally invasive procedure. This reamer, like all those of the traditional prior art reamers generally includes a reaming or scraping portion, which are aligned substantially along a single meridian of a hemisphere, and stabilizing portions to assist in ensuring a selected reaming orientation. However, they further disclose at least two separately opposing and sharp hook shaped protective “wings.” The wing structures are part of the actual shape and design of this reamer for the purpose in theory to attempt to assist in removing the reamer to decrease soft tissue damage during reaming. In some embodiments however, the backside of the reamer itself is a continuous tapered rim. Additionally they disclose large open areas in the cutting portion of the reamer shell that, similar in purpose to Lechot, Desarzens, and White, is directed at being guided by more accurate visual conformation to achieve more precise reaming depth into the acetabular socket.
U.S. Pat. No. 5,462,548 A, by Pappas, and Buechel discloses an acetabular reamer with a more efficient locking mechanism. This invention is directed at preventing unintended separation of the reamer head from the reamer shaft when the surgeon is withdrawing the reamer head from the acetabular cavity. They also include a reamer shaft, a mounting cap, a locking spring, and a sleeve in this system. Although the primary intention is the improved locking mechanism, in theory, (although this is not disclosed) this would also decrease soft tissue damage because of not having to use other tools to retract and explore the acetabular cavity to retrieve an unintentionally disengaged reamer head.
Henceforth, as can be clearly seen, the prior art does not provide any device or adequate method that specifically addresses all these issues by having all the benefits with none of the detriments. Therefore, there remains the risk of tissue damage and consequent problems caused by the flat shape and sharp, steep edges of the backside of the primary common use acetabular grater shell components during their extraction from the surgical site. Even the protective “wings” mentioned in one of the aforementioned prior art does not adequately address this issue. In fact due to the deficient continuity and separate hook shape of the wings, they in fact will cause the opposite effect by grabbing soft tissue during rotation and during the ingress and egress of the reamer causing more tissue damage than the normal traditional reamers. Furthermore, even in its alternative embodiments, that invention would be more costly to surgical facilities and orthopedic companies because it requires a total abandonment of all the prior art reamers in current use and a total redesign since this is itself a reamer. Therefore, there remains a great need for a safe, effective, cost efficient and universal adapter that can be applied to any size and style of acetabular graters. The present application addresses all these issues by enabling each insertion and extraction of the acetabular graters to be performed relatively quickly and easily, while avoiding and minimizing damage to soft tissues that have been caused by all the prior art shell components. This present application herein causes a positive domino effect by decreasing the time for completion of surgery, thereby decreasing the time the patient is under anesthesia, which then decreases unnecessary risks to the patient including but not limited to decreasing the risk for unintended soft tissue and vascular damage. This also decreases the physical force needed to extract the acetabular grater which then helps prevent further damage to soft tissues. By default this quicker and easier extraction then does not fatigue or frustrate the surgeon, and helps prevent other related problems. The present application is also inexpensive to mass produce and is cost effective for the patient and the medical facility. Additionally, the preferred embodiment of the present application does not require any modification to the prior art acetabular grater or its components, nor does it change the sterilization process, the surgery technique, or the appearance of the acetabular grater shell component on X-ray fluoro during the reaming procedure.